Hey Jeff, different CSU according to the Vital "First Ride" article linked below:

"the new Z1 houses 36mm stanchions and one of the heftiest crowns found in the industry. The stanchions are made from 6000-series alloy which and are thicker than other 36mm stanchions on the market. With the combination of thicker 36mm stanchions and a burly crown, the Z1 holds true to the mentality of stiffness over gram shavings."

"the largest difference between the Marzocchi Z1 and FOX 36 is the overall burliness of the uppers. This is very evident with a side-by-side comparison of the crowns. The Z1 is simply much thicker. In addition to that, the tubes are thicker as well. So much thicker that Marzocchi has their own diameter volume spacer."